Vehicles such as cars usually incorporate front and/or rear bumpers made of plastic with an inner metal reinforcing cross-member. Reinforcing cross-members or beams of different shapes (curved or straight) and of different cross-sections are known. The cross-sections may be open or closed. A closed cross-section generally provides greater stiffness to the elongated body than an open cross-section does.
Bumper beams are generally joined to the structure of the vehicle by means of impact absorbers, which are designed to deform in the event of impact absorbing the greatest possible amount of energy.
Bumper beams of closed cross-section may be formed out of a single metal plate (blank) which is deformed such as to form a substantially closed cross-section. One side of the metal plate may then be joined to another side. Alternatively, two metal plates may be deformed and then joined.
US 2008/217934 discloses a bumper beam including two tubular bodies formed by tube hydroforming that extend left and right. The tubular bodies are joined to each other in a parallel state. The tubular bodies each have a rectangular vertical cross-section shape including top and bottom and front and rear sides. The tubular bodies are disposed in a line from top to bottom, and opposing surfaces thereof are joined together across the entire length in the longitudinal direction.
JP 2002 087186 discloses a bumper beam for automobile formed in a tubular structural body without requiring a welding process and having an impact resistance. This bumper beam 1 comprises a front piece 1a, an upper piece 1d connected to the upper end of the front piece 1a, an upper intermediate piece 1e positioned on the lower side of the upper piece 1d, an upper side joint piece 1f connecting the rear end of the upper piece 1d to the rear end of the upper intermediate piece 1e, a lower piece 1g connected to the lower end part of the front piece 1a, a lower intermediate piece 1h positioned on the upper side of the lower piece 1g, and a lower side joint piece 1i connecting the rear end of the lower piece 1g to the rear end of the lower intermediate piece 1h. 
DE102005034520 discloses a unit (1) which comprises a transversally positioned u-profile (3) accommodating the front ends of two carrying elements (5) in the space between the outer segments (7,8). The carrying elements (5) have a square cross section and are assembled of a c-profile (11) and a flat bar (12) inserted between the edges of the outer segments of the profile (11). The edges of the profile (11) are provided with rows of hook-shaped extensions to be engaged with a row of slots positioned along the edges of the flat bar (12)
Vehicles such as cars may further contain rocker panels that are located below the vehicle doors. The rocker panels may cover the sides of the vehicle frame and may be covered by a rocker molding. They may sometimes be referred to as sills.
Rocker panels usually have a closed cross-section formed by two separate metal blanks. These blanks may be of different materials. The rocker panels may comprise an internal reinforcement member.
Both in the case of rocker panels and in the case of bumper beams joining may include welding, such as e.g. spot welding or laser beam welding. Such welding processes may be continuous or discontinuous i.e. in discrete points. Depending on the welding method chosen, the speed of manufacturing, the cost of manufacturing and the quality of the joint may be affected. Discontinuous spot welding e.g. requires an overlap of material.